Wireless communication devices, such as cellular telephones, PDAs, wireless adapters, communications-equipped computers or laptops, and the like, typically contain one or more antennas coupled to a radio frequency (RF) front end to support radio transmission and/or radio reception. To facilitate improved performance, multiple antenna systems can be used in mobile wireless communication devices. Multiple antenna systems can be used for various purposes such as separating transmit and receive functions, facilitating communication over multiple frequency bands and/or communication modes, antenna diversity, multiple-input multiple-output (MIMO) schemes, smart antenna systems, beam-forming, space-time coding, and the like.
Many different frequency bands in the range from 700 MHz through to 2500 MHz are now being allocated for cellular radio communication and users increasingly expect to be able to use whichever frequency band is available in any location. Additionally, there is also a trend for compact wireless communications devices.
Current wireless communication standards, such as the Universal Mobile Telecommunication System (UMTS) standard and the related Long Term Evolution (LTE) project, have proposed using multiple antenna technologies such as MIMO for communication in certain frequency bands. However, support for MIMO may only be required in a certain subset of frequency bands, and this subset may change by region. Furthermore, a multi-mode mobile device may be required to support additional standards, such as Global System for Mobile Communications (GSM), Wi-Fi, Wi-MAX, CDMA2000, or various other communication standards. Emerging standards utilize diversity reception and specifically, MIMO reception. For example, LTE, an emerging standard, specifies MIMO diversity reception.
Several multi-antenna solutions supporting antenna diversity or MIMO in at least one mode have been proposed in the art. One feature of such prior art solutions is that they typically rely on a main antenna for both transmitting and receiving operation at multiple frequencies, plus one or more secondary antennas which support diversity features when required e.g. when the main antenna finds itself in a multipath cancellation null. The secondary antennas may be smaller and lesser performing relative to the main antenna and still perform this function adequately. However, this approach has several drawbacks. First, since the main antenna is dissimilar to the secondary antenna, implementation of diversity or MIMO schemes can be challenging. Second, the main antenna must be sufficiently operable over a wide frequency band, which requires sophisticated design and a potentially large main antenna footprint. This can work against limitations on cost and/or antenna package size.
As the data rate of wireless systems increases through techniques such as advanced time-space coding and complex modulation schemes, the need for more complex radio frequency (RF) front-end and antenna systems becomes more critical, particularly in targeting the current multiplicity of wireless systems and their frequency bands of operation.
Therefore there is a need for a multiple antenna system for operation with a front end for a mobile wireless communication device that is not subject to one or more of the limitations of the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the invention.